The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to form secondary side power supply controllers. These secondary side power supply controllers typically were used to control power transistors connected to the secondary windings of a power supply system in order to control the output voltage on that particular secondary winding. Examples of such secondary side power supply controllers include the LT3710 offered by Linear Technology Corp. of Milpitas Calif. and the UT1584 offered by Texas Instruments Corp. of Dallas Tex. and formally offered by Unitrode Corp. of Merrimack N.H. One problem with these prior secondary side power supply controllers was propagation delay between detecting enablement of the primary power transistor and enabling the secondary side power transistor. This propagation delay limited the usable operating frequency of the secondary side power supply controller and resulted in poor regulation. Additionally, these prior secondary side power supply controllers generally regulated the secondary side output voltage with a limited duty cycle that could not achieve a full range of duty cycles. The limited duty cycle generally could not achieve a duty cycle that approached either zero or one hundred per cent which often resulted in poor regulation.
Accordingly, it is desirable to have a secondary side power supply controller and method that minimizes delay between the primary and secondary transistors, that facilitates an increased duty cycle operating range, and that can facilitates achieving a near zero per cent and near one hundred per cent duty cycle.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention.